Electrically powered incandescent lights are well known. However, such incandescent lights suffer from an inefficient conversion of electricity to visible light, using excess energy, producing excessive heat, and emitting significant amounts of radiation in, or near, the infrared spectrum. Therefore, the subject being illuminated is often heated as well as illuminated, particularly with high intensity incandescent lights. The heat generated by incandescent lighting may burden environmental control systems, such as air conditioning systems. The combination of inefficient light generation and excess heat generation may lead to higher operating costs, for example, unnecessarily large electric utility bills. In addition to excess power use, using such lights in operatory to illuminate a patient, may result in heating and drying illuminated tissue, causing discomfort to the patient.
More recent alternatives to incandescent light emitting elements include fluorescent light bulbs, which generate less heat than incandescent bulbs. However, fluorescent bulbs tend to be bulky and generally produce light of a less desirable color and intensity for many applications. In addition, the electrical components of fluorescent bulb circuitry, such as the ballast, tend to be bulky and produce undesirable noise. In use in an operatory, it is generally desirable to reduce the bulk of a lamp fixture, to reduce its intrusion into the operating arena, and to facilitate ease of manipulation of the lamp fixture.
Most dental exam lights use incandescent bulbs as light sources, and therefore produce some or all of the undesirable side effects described above. While some of these lights have been designed to mitigate some of these disadvantages, such as filtering emission of infra-red (IR) or providing cold-mirrors to prevent excessive warming of the patient and user, they still suffer from, for example, relatively short bulb life-time, inability of the user to adjust light color temperature and chromaticity of light, color temperature becoming lower and the light becoming “warmer” (shifting from white to orange/red) when light intensity is reduced (dimmed), and production of significant ultraviolet (UV) and blue light which may cause undesired and uncontrolled curing of dental composites and adhesives.
More recently, light emitting diode (LED) based dental exam lights have been introduced, for example, U.S. Pat. No. 8,016,470, herein incorporated by reference in its entirety. A lamp according to U.S. Pat. No. 8,016,470 is shown by FIG. 1. The lamp 100 is powered by electricity, and functions to provide illumination to a work area disposed a distance from the lamp front 102. The lamp 100 may include an attachment structure (not shown) connecting the lamp 100 to a suspension structure (not shown) in the work area. Such an attachment structure is typically attached at a back 106 of the lamp 100. A typical suspension structure (not shown) in a dental operatory permits a user to orient the lamp 100 in space operably to aim the light output of lamp 100 at the desired target area. Optional attachments, such as a shield (not shown), or a portion of a lamp base (not shown), can be hinged, or otherwise openable by a user, to provide access to the interior of lamp 100 for maintenance or replacement of a light generating element, for example, an LED 118.
A reflecting element 116 directs the light of the LED 118 output toward a target. The reflecting element 116 is a concave aspheric reflector which collects the light emanating from a light mixing rod 136 secured in place by a rod support 138 and focuses the collected light onto the plane of the patient's face (“image plane”). The LEDs 118 are mounted onto a bracket 112 associated with a lamp housing 114. The bracket 112 assembly includes connection structure for the electricity supplied to the LED 118 and may further include a metal core circuit board 130. The bracket 112 is formed from a heat conducting material and further dissipates heat with heat conducting pipes 134, heat sink fins 142, and via convection through a gap 144 between the reflecting element 116 and the heat sink 142.
While the prior art LED dental lamps improve upon some aspects of incandescent lamps, the positioning of the LED and associated circuitry at the lamp front still presents problems. For example, the LED assembly may block light from the reflector. Further, this configuration places the hot LED assembly at the portion of the lamp that is closest to the patient, and requires additional design and materials to conduct the heat away from the patient. In addition, the arrangement necessitates electrical connectivity to the LED assembly at the lamp front. Finally, the location of the LED assembly and associated heat and electrical conduits in the lamp front may result in additional size and weight of the lamp. Therefore, there is a need in the industry for an LED dental lamp that addresses the above shortcomings.